Highlight Topic: Understanding the North Sea

A new Internet portal, coastMap, has been created at the Helmholtz-Zentrum Geesthacht (HZG) in recent years. coastMap enables scientists as well as the interested public to access a wealth of scientific information about the North Sea. The portal is based on hundreds of thousands of measurement data that can be linked to computer models to provide an overall picture of the North Sea. The results can be downloaded in the form of descriptive maps. This data can assist environmental policy makers or can also be used for environmental education.

Measurement data on sediments, water and the atmosphere are fed into the coastMap portal (Photo: Dirk Hellriegel)

Coastal research is a challenge, as the sea is always partially inaccessible. A great deal of effort is required to obtain samples from the sea and the coasts. Ship travel is required, as a crane or winch to lower the measurement instruments is needed to take soil samples or measure the water properties at different depths. Despite all this effort, such measurement cruises do not provide sufficient insight: they result in measurement values of individual, tiny dots in the vast coastal sea. If, however, we want to know the status of the coastal sea in general — for example, how heavily it is effected by pollutants or excess nutrients from the agricultural sector, then we need an overview of the coastal sea in its entirety. Data, however, from merely a few measurement points in the sea can hardly provide this information.

To obtain an overall impression of the entire German North Sea in the future, the Helmholtz-Zentrum Geesthacht (HZG) has developed the coastMap internet portal in recent years, which extracts substantially more from conventional measurement data than previously possible: the research cruise data is fed into numerical models by experts and these models can then simulate the situation across the entire North Sea. The models assess the condition of the complete region with the help of the selective measurement values from the sea.

More than a thousand different measured variables

Point measurement values are combined with model data. (Screenshot: coastMap)

The portal is particularly attractive because the data is provided not only numerically, but can also be vividly displayed in the form of digital maps. The computer model results can additionally be imaged and processed. All in all, the user can search for more than one thousand different measurement variables in coastMap, including pollutant concentrations in the water; the size of sand and silt particles on the seafloor; or the concentration of chlorophyll (plant pigment) in the water, an indication as to the amount of phytoplankton present. The user interface for analysing data from the computer models is of particular interest for the experienced user. This interface is called the Model Analysis Tool, where different maps and data can be added and superimposed to illustrate connections. Using this method, for example, maps pertaining to nutrients in the water can be combined with chlorophyll maps. The user can therefore derive the extent to which the pollutants contribute to algal growth.

“The portal is aimed at scientists as well as the interested public,” says Marcus Lange, one of the coastMap project managers. “Researchers can quickly and easily search for measurement values to answer particular scientific questions. Teachers can, for example, find data for their lessons on pollutant distribution in the North Sea, and they can then have their students continue to process the data within the framework of projects in these school lessons.” In addition, the maps provide government representatives and politicians vital information, which can serve as a foundation for political decisions.

Understanding the consequences of interfering with the environment

Prof Kay-Christian Emeis, director of HZG’s “Biogeochemistry in Coastal Seas” division within the Institute of Coastal Research, conceived the coastMap idea a few years ago. He wished to make the results of a research project (Link to NOAH) publicly available, results in which the experts from the Institute of Coastal Research and its partners in science and the governmental sector had mapped different types of North Sea soil in detail. In the North Sea there are, for example, firm sandy areas, consisting of large grains, and there are also silty sediments comprised of small particles. These different types of sediment are home to various communities of life forms and exchange chemical compounds and nutrients with the water in a certain manner. Because the seabed in the North Sea is used more and more extensively for fishing, wind park construction or the removal of sand for beach nourishment, a comprehensive overview of the seafloor is extremely vital. This overview is required not least for enabling researchers to assess what consequences fisheries, wind park construction and sand removal could have on certain sediments and the surrounding sea.

In the meantime, the portal’s measurement variables have been greatly expanded. Nitrogen, for example, is a particularly important parameter for plant nutrition. It is an interesting chemical element because it is present in nature in different chemical compounds and is converted again and again by bacteria and plants in a cycle, transforming from one form to another.

Algal blooms in the North Sea (Photo: Sabine Billerbeck)

Nitrogen comprises 78% of the atmosphere. Most plants, however, cannot utilise pure nitrogen. They depend on bacteria to convert atmospheric nitrogen in several steps into the nitrogen compound nitrate, which can then be utilised by the plants. Nitrate thereby works as a fertiliser — both for plants on land and for algae. The problem today is, with faecal matter from wastewater and surplus fertiliser from fields, a great deal of nitrate winds up in the rivers and ultimately in the sea. This process is called eutrophication. The nitrate causes unnaturally heavy algal growth. The algae sink when they die and are broken down by bacteria that consume oxygen. If too much algae are present, the bacteria are particularly active, whereby a large quantity of oxygen is consumed. This can lead to an oxygen deficiency in the water. In these areas, higher organisms — such as fish, crabs and mussels — will die.

The portal eases the researchers’ work

Sample of a small sediment core (Photo: Andreas Neumann / HZG)

Fortunately, nitrate can be broken down into pure nitrogen by microorganisms, which counteracts the eutrophication. This process is called denitrification and takes place mainly in the sediment. With the help of coastMap, biologist Dr Andreas Neumann has now precisely studied in which North Sea sediments nitrate degrades particularly well. “This insight is vital because we can use it to determine which sediments are especially important for denitrification and should be protected from sand removal measures,” says Dr Neumann. Without coastMap, his work would have become extremely difficult as he required many different measurement variables for his analyses, which included values pertaining to how permeable the sediment is for water and chemical substances; values for the water’s current velocity; and, of course, values for nitrogen concentration in the seabed.

Dr Andreas Neumann, together with his colleagues, sailed on a research vessel to collect and measure samples in the North Sea. This endeavour alone, however, was insufficient. On the one hand, because he couldn’t measure all required variables himself, and on the other hand, because a person cannot measure the entire North Sea. Thanks to coastMap, he could supplement the missing data. “What is special about coastMap is that measured values from different databases and from numerous research expeditions, which were previously separate, were now combined,” says Dr Neumann. “Earlier we needed to round up data from many different archives to locate what we required. Now I can retrieve it with a few clicks on a single website.”

The work carried out by his colleagues in modelling was also helpful to Dr Neumann. They calculated the distribution of nitrate and denitrification for the entire North Sea based on measurement data. “Modelling, however, isn’t everything,” says Dr Carsten Lemmen, who is a specialist in modelling ecosystems at the Institute of Coastal Research. “Easy extraction of the desired information from the vast quantity of data produced by the computer models is also highly important. If you use models to examine the development in the North Sea over a longer period of time, a great deal of data is generated. Finding the relevant values can be extremely time-consuming for external research colleagues.” Sometimes you only need a few numerical values for a very specific date, which you first need to extract from the datasets.

His colleague, geoinformatics scientist Dietmar Sauer, who made coastMap work on a technical level, elaborates: “We have therefore linked all measured datasets and model data in coastMap in such a way that you can search for specific values for specific days or time periods. Colleagues who use coastMap can therefore achieve their goal much more rapidly.” Dr Andreas Neumann also profited here. In a relatively short time, he had collected all the measurement parameters and values required that enabled him to determine which sediments play a special role in nitrate degradation. His results showed that the permeable coarse sands along the North Sea coast are particularly important.

A new understanding of coastal sea processes

The coastMap portal allows users to selectively search data, link this data together, and display it as a clearly imaged map. This can lead to previously undiscovered connections. What exerts an influence on which measurement variable? How does wind park construction impact currents, nutrient distribution, algal growth or the subsequent breakdown of algal masses? Such complex correlations are now possible. Dr Carsten Lemmen views utilising coastMap as a further benefit not only for staff at the Helmholtz-Zentrum Geesthacht, but also for scientists at other institutions: “coastMap can support scientific exchange. We’re open to interesting research questions that colleagues introduce. It’s especially interesting when colleagues from entirely different disciplines come together.”

Dr Justus van Beusekom at the Institute of Coastal Research, who deals extensively with the exchange of nutrients between water, sediment and marine life, emphasises another coastMap strength: “Thanks to the computer models, it is possible to look into the future and to draw conclusions from the present situation to the future.” Model data in coastMap can be used, for example, to determine how the North Sea’s nutrient budget changes if we reduce nitrate input from rivers. Would the North Sea habitat profit from such action, as algal blooms and the accompanying oxygen deficiency would become less frequent? Such future scenarios are especially vital because they could assist in determining appropriate environmental policy decisions,” says Dr van Beusekom. For example, does it make sense to impose restrictions on the agricultural sector and reduce fertiliser quantities? Van Beusekom explains, “Our colleagues in the ‘System Analysis and Modelling’ division can estimate the success of such measures using model calculations.”

Decision making assistance in environmental policy

Good environmental status of the marine environment is to be achieved. (Photo: Dirk Hellriegel)

Such decision making aids are, for example, vital in preparing regulations for marine protection as stipulated in the European Marine Strategy Framework Directive (MSFD). This framework prescribes that “good environmental status of the marine environment” in European seas should be achieved by 2020. In simple terms, this means that the state of the seas should improve in the future due to the MSFD. How this “good environmental status” will look in individual cases, however, and what measures must be taken to achieve this goal remains in part unclear. “If scientists can use model calculations to assess the impact of an environmental measure, this will be of enormous assistance to policy makers,” says Dr van Beusekom. This is particularly true if the model calculations and scenarios are based on a wealth of real measurement data, as compiled in coastMap.

What is also especially important for all of this data is that it is incorporated in a similar format into the coastMap system and, to this end, that an abundance of what is known as “metadata” is provided. Metadata is accompanying information that provides background on the actual measured value. It can be compared to the postal address of the recipient and sender on an envelope. The letter contains the actual message, but without the recipient or sender information, it is useless because the letter cannot be categorised. The measurement metadata includes time and location, name of the researcher as well as information such as water depth at which the value was taken. This uniform metadata is vital in enabling compilation and comparison of measured values from various sources.

Exciting research stories

The unique ecosystem in the North Sea is a Spotlight topic (Graphic: Glynn Gorrick)

Originally coastMap was envisioned as a tool by scientists for scientists. As coastMap contains a treasure trove of knowledge about the North Sea, it became quickly evident, however, that it could also be of interest to the public, decision makers and planners on the coast, or for journalists. Results from the coastMap project that are especially compelling are therefore outlined in the portal under the “Spotlight” section. Here, for example, the user will find interesting facts about how the sensitive Wadden Sea can be better protected from an oil spill during an accident. The spread of shipping exhaust gases is also explained in detail.

The coastMap experts wish to continue expanding the portal in the future, according to Marcus Lange: “coastMap has meanwhile also added a great deal of data from marine regions other than the North Sea and can now be used by colleagues who deal with these marine regions. We have even incorporated data for the Chinese Bohai Sea, as many problems we see in the North Sea also occur elsewhere.“